Update repositories.txt (#5861)

added LIN_slave_portable_Arduino

Author: gicking

repositories.txt

@@ -2611,6 +2611,7 @@ https://github.com/giannivh/SmoothThermistor
 https://github.com/Gibartes/uCOS-II_Arduino
 https://github.com/gicking/LIN_master_Arduino
 https://github.com/gicking/LIN_master_portable_Arduino
+https://github.com/gicking/LIN_slave_portable_Arduino
 https://github.com/gicking/NeoHWSerial
 https://github.com/gigabits-org/gigabits-arduino
 https://github.com/gigix74/CalibratedSpeed